OO Design Principles Compilation

OO Design Principles Compilation: "

This page is a work in progress… a compilation of information about object-oriented design principles and values.

S.O.L.I.D. Class Design Principles

Collected by Robert C. Martin for his book “Applying Principles and Patterns”

Single Responsibility Principle (SRP)

A class should have only one reason to change. For example, if a change to the business rules causes a class to change, then a change to the database schema, GUI, report format, or any other segment of the system should not force that class to change.

• http://davidhayden.com/blog/dave/archive/2005/05/29/1066.aspx


• http://c2.com/cgi/wiki?SingleResponsibilityPrinciple


• Head First Design patterns page 185, 336, 339, 367


• http://msdn.microsoft.com/en-us/magazine/cc546578.aspx


• http://codebetter.com/blogs/david_laribee/archive/2008/09/09/why-solid-gimme-an-s.aspx

Open/Closed Principle (OCP)

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

• http://davidhayden.com/blog/dave/archive/2005/06/04/1096.aspx


• http://en.wikipedia.org/wiki/Open/closed_principle


• Head First Design patterns page 86-87, 407


• http://c2.com/cgi/wiki?OpenClosedPrinciple


• http://codebetter.com/blogs/david_laribee/archive/2008/09/11/why-solid-gimme-an-quot-o-quot.aspx

Liskov substitution principle (LSP)

Subtypes must be substitutable for their base types. If class A inherits from class B, then wherever you can use A you should be able to use B. E.g. remember that square is not necessarily a rectangle! When extending: Preconditions cannot be straightened, Postconditions cannot be loosened, visible Invariants cannot be changed (?). Invariants: users depend on this both before and after sending a message. Use a proper set-based inheritance relationship. Not following set semantics is very risky. Subsumption Rule: A reference to a subtype can be used in any context where a reference to a super type is expected. This principle extremely limits what SHOULD be done with the pure extension (inheritance) mechanism. Do not follow at your own risk.

• http://davidhayden.com/blog/dave/archive/2005/06/10/1226.aspx


• Agile Principles and Patterns page ?


• http://c2.com/cgi/wiki?LiskovSubstitutionPrinciple


• http://en.wikipedia.org/wiki/Liskov_substitution_principle


• http://javaboutique.internet.com/tutorials/JavaOO/


• http://codebetter.com/blogs/david_laribee/archive/2008/09/22/why-solid-gimme-an-l.aspx

Interface Segregation Principle (ISP)

The dependency of one class to another one should depend on the smallest possible interface.

• http://davidhayden.com/blog/dave/archive/2005/06/15/1482.aspx


• http://c2.com/cgi/wiki?InterfaceSegregationPrinciple


• http://www.google.com/search?q=interface+segration+principle


• http://doodleproject.sourceforge.net/articles/2001/interfaceSegregationPrinciple.html

Dependency Inversion Principle (DIP)

Depend upon abstractions (interfaces), not upon concrete classes.

• http://davidhayden.com/blog/dave/archive/2005/06/10/1261.aspx


• http://en.wikipedia.org/wiki/Dependency_inversion_principle


• Head First Design patterns page 139-143


• http://c2.com/cgi/wiki?DependencyInversionPrinciple

Other Important Ones

Law of Demeter

aka Principle of Least Knowledge: Only talk to your friends

Any method M of an object O may only invoke the methods of the following kinds of objects:

• itself


• its arguments/parameters


• any objects it creates/instantiates


• its direct component objects

See

• http://en.wikipedia.org/wiki/Principle_of_Least_Knowledge


• http://ctrl-shift-b.blogspot.com/2008/06/distilling-law-of-demeter.html


• Head First Design patterns page 265

Hollywood Principle

Don’t call us, we’ll call you.

• http://en.wikipedia.org/wiki/Hollywood_Principle


• Head First Design patterns page 296

Don’t Repeat Yourself (DRY)

Remove duplication.

• Pragmatic Programmer page 27


• http://en.wikipedia.org/wiki/Don%27t_repeat_yourself


• http://c2.com/cgi/wiki?DontRepeatYourself

Program to an interface, not an implementation

Maybe just another way to say dependency inversion.

• Head First Design patterns page 11, 110-111, 243, 335


• http://www.artima.com/lejava/articles/designprinciples.html

You Ain’t Gonna Need It (YAGNI)

Do not add code that you “think will be used later”. Add code only at “Last Responsible Moment”

• http://c2.com/xp/YouArentGonnaNeedIt.html


• http://en.wikipedia.org/wiki/You_Ain%27t_Gonna_Need_It

Keep It Simple, Stupid (KISS)

What is the simplest thing that could possibly work?

• http://c2.com/cgi/wiki?DoTheSimplestThingThatCouldPossiblyWork


• http://en.wikipedia.org/wiki/KISS_principle

And More

Encapsulation and Information Hiding

http://en.wikipedia.org/wiki/Encapsulation_(computer_science) http://en.wikipedia.org/wiki/Information_hiding

Separation of Concerns (SoC)

http://ctrl-shift-b.blogspot.com/2008/01/art-of-separation-of-concerns.html

High Cohesion

http://en.wikipedia.org/wiki/Cohesion_(computer_science)

Low/Loose coupling

• Head First Design patterns page 53


• http://en.wikipedia.org/wiki/Coupling_(computer_science)

Convention over Configuration (CoC)

http://en.wikipedia.org/wiki/Convention_over_Configuration

Command-query separation (CQS)

• http://en.wikipedia.org/wiki/Command-query_separation


• http://martinfowler.com/bliki/CommandQuerySeparation.html

[edit] Design by Contract (DbC)

• http://en.wikipedia.org/wiki/Design_by_contract


• http://c2.com/cgi/wiki?DesignByContract

Dependency Injection (DI)

Inversion of Control (IoC)

Avoid Fragile Baseclass

http://en.wikipedia.org/wiki/Fragile_base_class

Has-a Is-a

http://en.wikipedia.org/wiki/Has-a http://en.wikipedia.org/wiki/Is-a http://en.wikipedia.org/wiki/Object_composition

What is Identity

http://en.wikipedia.org/wiki/Identity_(object-oriented_programming)

Interchangeability

http://en.wikipedia.org/wiki/Interchangeability_(computer_science)

Option-operand separation

http://en.wikipedia.org/wiki/Option-operand_separation

Intention Revealing Names

• http://c2.com/cgi/wiki?IntentionRevealingNames


• http://www.hanselman.com/blog/ProgrammerIntentOrWhatYoureNotGettingAboutRubyAndWhyItsTheTits.aspx

Zero Friction Development

http://www.google.com/search?q=Zero+Friction+development

Encapsulate Variation

Separate what varies from what stays the same. Also known as Serenity Principle.

• http://blogs.msdn.com/steverowe/archive/2007/12/26/encapsulate-what-varies.aspx


• Head First Design patterns page 9, 111

Composition over inheritance

• Head First Design patterns page 23, 243, 397

Common Closure Principle

Classes that change together must be placed in the same package.

• http://c2.com/cgi/wiki?CommonClosurePrinciple

Comments"